Yep, these two behaviors are the same in the original MS-DOS game. Robots were always sluggish to react to far-away players. Even though that's probably unrealistic, if we made them more aggressive, many levels would unintentionally become very difficult. As for the Fusion Cannon, it fires big projectiles with big hitboxes. This makes it easy to hit several robots with one shot, but the balancing factor is that the projectiles often clip the corners of walls and explode - which often happens to that Miniboss's projectiles.

All weapon fire are projectiles. Some of them just have graphics that make them look like vague blobs.

For the reactor, can you provide specific steps to reproduce? Identify an affected level, how to enter that state, etc.

Many variables are not included in the save. In my opinion, this is because save-sensitive data was added haphazardly without adequate consideration for what needed to be saved and what could be recomputed on load. Unfortunately, the save file format is very difficult to extend without breaking backward compatibility. It is not impossible to extend, but it is ugly, particularly for any polyinstantiated data (per-object, per-segment, per-wall, etc.). I have planned for a long time to completely replace this, but I have some other big projects in the queue ahead of it.